Pipes, Cisterns and Work, Time

Concepts Covered The typical questions that appear from this topic are word problems. The basic concept tested in this chapter is analogous to the concepts tested in Speed Time Distance. So, if you have a good grasp of Speed Time Distance topic, then you will be able to understand and solve questions in this topic with a lot of ease. 4GMAT's GMAT Math Lesson Book in this chapter covers the following concepts:

1. The chapter begins with the rules governing the questions in pipes and cisterns and it is explained with illustrative examples
2. There are 17 solved examples in questions related to pipes and cisterns. Some of the tough math questions in this topic are featured here.
3. The concepts regarding work and time are explained with examples.
4. There are 13 solved examples for questions related to work and time. Shorcuts to few hard math questions in work time are provided.
5. 24 exercise problems in both pipes and cisterns as well as work and time have been provided with the answer key and explanatory answers to the questions
6. An objective type speed test with around 50 questions with explanatory answers and answer key provided for the speed test

Here is an example of a typical solved example in this chapter.
Sample Question
Question
Pipe A fills a tank in 30 minutes. Pipe B can fill the same tank 5 times as fast as pipe A. If both the pipes were kept open when the tank is empty, how much time will it take for the tank to overflow?

Explanatory Answer
Pipe B fills the tank 5 times as fast as pipe A.
Therefore, pipe B will fill the tank in one-fifth of the time that pipe A takes.
Pipe B will fill the tank in 30 / 5 = 6 minutes.
In 1 minute, pipe A will fill 1 / 30th of the tank and pipe B will fill 1 / 6th of the tank.
Therefore, together, the two pipes will fill (1/30 + 1/6) = (1+5 / 30) = 6/30 = 1/5th of the tank in a minute
Hence, the two pipes working together will take 5 minutes to fill the tank.